Small fix for fpm_model

[St-Maxwell]

I found fpm will crash when executing fpm build --show-model, if there are empty source files in project.

After looking into code, I found parse_f_source returns an instance of srcfile_t with its allocatable members uninitialized for empty source files.

! Ignore empty files, returned as FPM_UNIT_UNKNOWN
if (len_trim(file_lines_lower) < 1) return

As a result, in info_srcfile function, an error will occur when printing srcfile_t objects with FPM_UNIT_UNKNOWN type.

So I make it skip for FPM_UNIT_UNKNOWN type.

[LKedward]

Thanks for spotting this @St-Maxwell - quick question: would deleting the if (len_trim(file_lines_lower) < 1) return line also solve this problem? Then maybe parse_f_source would just allocate zero-length arrays

[St-Maxwell]

@LKedward Thanks for replying. I think it is OK to remove if (len_trim(file_lines_lower) < 1) return and add an extra change to the next statement, because fnv_1a requires a non-zero-length arrays. If this change is preferred, I will update my commit.

from

! Ignore empty files, returned as FPM_UNIT_UNKNOWN
if (len_trim(file_lines_lower) < 1) return

f_source%digest = fnv_1a(file_lines)

to

! Ignore empty files, returned as FPM_UNIT_UNKNOWN
!if (len_trim(file_lines_lower) < 1) return

if (len_trim(file_lines_lower) >= 1) f_source%digest = fnv_1a(file_lines)

[LKedward]

Thanks okay yes I think this would be preferred; my reasoning for this is to ensure that parse_f_source always returns the 'same' thing (ie all components allocated), so that we don't need to repeatedly code special statements everywhere else in the code.

[LKedward]

Many thanks for this fix @St-Maxwell. All looks good to me 👍